The present invention relates to an optical sensor and, more particularly, to an optical pressure sensor comprising a photoelastic material.
In a conventional optical pressure sensor using a photoelastic material, since the photoelastic material is fixed on a pedestal by an adhesive material or a binder, so that the portions of the photoelastic material in contact with the pedestal are tightly secureed on the pedestal, internal stress may be produced from the portions of the photoelastic material adhered to or bound on the pedestal when the adhesive or the binder is hardened. After the adhesive or the binder hardens, the internal stress remains in the connections between the photoelastic material and the pedestal. The internal stress widely deflects detecting characteristics of a pressure. If the coefficient of thermal expansion in the photoelastic material is not equal to that of the pedestal in an operational temperature range, the difference between the coefficients of thermal expansion in the photoelastic material and the perdestal causes another internal stress and thereby causes a change in the quantity of passing light. Further, when a load is applied to the photoelastic material, the stress may be concentrated upon the connection portions between the photoelastic material and the pedestal, in addition to the pressing position, so that the pressure sensitivity may be decreased.